Week 3

Question 1

What’s a reaction mechanism?

Answer 1

A reaction mechanism is an educated guess about the way a reaction occurs

Question 2

Describe the rate of the reaction:

Answer 2

The rate of the reaction describe how fast does a reaction occurs (how fast the concentration of reactants decrease and the concentration of products increase)

Question 3

What’s the half life of a reaction?

Answer 3

The time taken for a concentration of a given reactant to reach half of its value.

Question 4

Describe what happens at the half life of 0th order reaction:

Answer 4

For 0th order reaction the half life decreases as the concentrations of reactants decreases.

Question 5

Describe what happens at the half life of 1st order reactions:

Answer 5

For 1st order reaction the half life remain constant with time.

Question 6

What is diffusion coefficient:

Answer 6

Diffusion is the rate at which molecules encounter with one another.

Question 7

What are the 4 parameters that affect diffusion?

Answer 7

1- Size of the molecules 2- Size of the sorroundings 3- Shape of the molecules and temperatures 4- Diffusion coefficient

Question 8

What are the three things that must happen at the molecular level in order for a reaction to occur?

Answer 8

1-Molecules must collide 2-Molecules must collide with the right orientation 3-Molecules colliding with the right orientation must have enough energy to overcome the activation energy barrier

Question 9

What’s Activation Energy?

Answer 9

The minimum energy a reactant molecule has to posses to initiate the bond cleavage and formation process.

Question 10

What’s a transition state?

Answer 10

Is an high energy species whose chemical character is between reactant and products. Transition state is the highest energy species that exists during the course of the reaction.

Question 11

What’s a catalyst?

Answer 11

A catalyst is a chemical species that lower the activation energy barrier, speeding up the rate of the reaction and it’s itself unchanged at the end of the reaction.

Question 12

What are enzymes?

Answer 12

Enzymes are highly efficient and specialized catalysts for one or more chemical reaction in a living system.

Question 13

Describe the molecular structure of enzymes:

Answer 13

They are usually globular proteins consisting of one long chain of amino acids folded into a spherical shape determined by non covalent intermolecular forces.

Question 14

What’s a cleft?

Answer 14

The site at which the substrate binds to the enzyme

Question 15

Why are enzyimes highly specific?

Answer 15

Because the shape of the cleft is complementary to the shape of the substrate so that only the substrate can fit into it.

Question 16

What’s a substrate?

Answer 16

Substrate is a molecule whose reaction is catalysed by an enzyme.

Question 17

Describe the active site in the cleft:

Answer 17

The active site is the region that exhibit the highest degree of complementarity with the shape of the substrate and participate to the strongest interaction with it.

Question 18

What’s induced fit?

Answer 18

A change in the shape of either the enzyme and the substrate (or both) that lower the activation energy.

Question 19

What happen at Vmax?

Answer 19

The enzyme is working at full capacity and it’s saturated (any active site has a substrate molecule bound to it).

Question 20

What’s Michaelis Constant (Km)?

Answer 20

Is the concentration of substrate required for an enzyme to operate at half its maximum velocity.

Question 21

Why is Km important?

Answer 21

It tells us about the strength of the interaction between the substrate and the enzyme.

Question 22

If Km is small…

Answer 22

The substrate binds strongly to the active site and the substrate is readily converted to products, even at low substrate concentration

Question 23

If Km is large…

Answer 23

The substrate binds less strongly to the enzyme and needs high concentration of substrate to catalyse effectively the formation of products.

Question 24

What’s enzyme inhibition?

Answer 24

Reduction of the rate of an enzyme catalysed reaction.

Question 25

Describe competitive inhibition:

Answer 25

Competitive inhibitors have a structure that is similar to that of the substrate and binds to the active site of an enzyme to form an enzyme-inhibitor complex.

Question 26

Describe Non-competitive inhibition:

Answer 26

Occurs when binding of an inhibitor affects the catalytic rate rather than the binding affinity of for the substrate. The substrate and the inhibitor bind at different site on the enzyme.

Question 27

What’s metabolism?

Answer 27

All the chemical changes as food nutrients are processed by an organism to release Gibbs free energy and form complex chemicals constituent of the living cell.

Question 28

What’s an exergonic reaction?

Answer 28

A reaction that release Gibbs free energy (ΔG<0). It’s spontaneous and products favored.

Question 29

What’s endergonic reaction?

Answer 29

A reaction that requires Gibbs free energy (ΔG>0). It’s non spontaneous and reactants favored.

Question 30

Describe the relation between exergonic and endergonic reactions in human body.

Answer 30

In human body, Gibbs free energy released by exergonic reaction is used to force endergonic reactions.

Question 31

Which are the three steps involved in metabolism?

Answer 31

1-Digestion 2-Reduction of small molecules into simple units. 3-Oxidation of acetyl group from Acetyl CoA to form CO2 and H2O (Citric Acid Cycle).